Commit message: Add a test for GENERAL_NAME_cmp

Based on a boringssl test contributed by David Benjamin

Reviewed-by: Tomas Mraz <tmraz@fedoraproject.org>
CVE: CVE-2020-1971
CWE: CWE-476
Vulnerability description: The X.509 GeneralName type is a generic type for representing different types of names. One of those name types is known as EDIPartyName. OpenSSL provides a function GENERAL_NAME_cmp which compares different instances of a GENERAL_NAME to see if they are equal or not. This function behaves incorrectly when both GENERAL_NAMEs contain an EDIPARTYNAME. A NULL pointer dereference and a crash may occur leading to a possible denial of service attack. OpenSSL itself uses the GENERAL_NAME_cmp function for two purposes: 1) Comparing CRL distribution point names between an available CRL and a CRL distribution point embedded in an X509 certificate 2) When verifying that a timestamp response token signer matches the timestamp authority name (exposed via the API functions TS_RESP_verify_response and TS_RESP_verify_token) If an attacker can control both items being compared then that attacker could trigger a crash. For example if the attacker can trick a client or server into checking a malicious certificate against a malicious CRL then this may occur. Note that some applications automatically download CRLs based on a URL embedded in a certificate. This checking happens prior to the signatures on the certificate and CRL being verified. OpenSSL's s_server, s_client and verify tools have support for the "-crl_download" option which implements automatic CRL downloading and this attack has been demonstrated to work against those tools. Note that an unrelated bug means that affected versions of OpenSSL cannot parse or construct correct encodings of EDIPARTYNAME. However it is possible to construct a malformed EDIPARTYNAME that OpenSSL's parser will accept and hence trigger this attack. All OpenSSL 1.1.1 and 1.0.2 versions are affected by this issue. Other OpenSSL releases are out of support and have not been checked. Fixed in OpenSSL 1.1.1i (Affected 1.1.1-1.1.1h). Fixed in OpenSSL 1.0.2x (Affected 1.0.2-1.0.2w).

Project: openssl

static int set_altname(X509 *crt, ...)
{
    int ret = 0;
    GENERAL_NAMES *gens = NULL;
    GENERAL_NAME *gen = NULL;
    ASN1_IA5STRING *ia5 = NULL;
    va_list ap;
    va_start(ap, crt);
    gens = sk_GENERAL_NAME_new_null();
    if (gens == NULL)
        goto out;
    while (1) {
        int type;
        const char *name;
        type = va_arg(ap, int);
        if (type == 0)
            break;
        name = va_arg(ap, const char *);

        gen = GENERAL_NAME_new();
        if (gen == NULL)
            goto out;
        ia5 = ASN1_IA5STRING_new();
        if (ia5 == NULL)
            goto out;
        if (!ASN1_STRING_set(ia5, name, -1))
            goto out;
        switch (type) {
        case GEN_EMAIL:
        case GEN_DNS:
            GENERAL_NAME_set0_value(gen, type, ia5);
            ia5 = NULL;
            break;
        default:
            abort();
        }
        sk_GENERAL_NAME_push(gens, gen);
        gen = NULL;
    }
    if (!X509_add1_ext_i2d(crt, NID_subject_alt_name, gens, 0, 0))
        goto out;
    ret = 1;
 out:
    ASN1_IA5STRING_free(ia5);
    GENERAL_NAME_free(gen);
    GENERAL_NAMES_free(gens);
    va_end(ap);
    return ret;
}

Project: openssl

static int set_cn3(X509 *crt, const char *name)
{
    return set_cn(crt, NID_commonName, name,
                  NID_commonName, "dummy value", 0);
}

Project: openssl

static int set_altname_dns(X509 *crt, const char *name)
{
    return set_altname(crt, GEN_DNS, name, 0);
}

Project: openssl

static int set_email2(X509 *crt, const char *name)
{
    return set_cn(crt, NID_pkcs9_emailAddress, "dummy@example.com",
                  NID_pkcs9_emailAddress, name, 0);
}

Project: openssl

static int check_message(const struct set_name_fn *fn, const char *op,
                         const char *nameincert, int match, const char *name)
{
    char msg[1024];

    if (match < 0)
        return 1;
    BIO_snprintf(msg, sizeof(msg), "%s: %s: [%s] %s [%s]",
                 fn->name, op, nameincert,
                 match ? "matches" : "does not match", name);
    if (is_exception(msg))
        return 1;
    TEST_error("%s", msg);
    return 0;
}

Project: openssl

static int set_altname_email(X509 *crt, const char *name)
{
    return set_altname(crt, GEN_EMAIL, name, 0);
}

Project: openssl

static int set_cn_and_email(X509 *crt, const char *name)
{
    return set_cn(crt, NID_commonName, name,
                  NID_pkcs9_emailAddress, "dummy@example.com", 0);
}

Project: openssl

static int test_GENERAL_NAME_cmp(void)
{
    size_t i, j;
    GENERAL_NAME **namesa = OPENSSL_malloc(sizeof(*namesa)
                                           * OSSL_NELEM(gennames));
    GENERAL_NAME **namesb = OPENSSL_malloc(sizeof(*namesb)
                                           * OSSL_NELEM(gennames));
    int testresult = 0;

    if (!TEST_ptr(namesa) || !TEST_ptr(namesb))
        goto end;

    for (i = 0; i < OSSL_NELEM(gennames); i++) {
        const unsigned char *derp = gennames[i].der;

        /*
         * We create two versions of each GENERAL_NAME so that we ensure when
         * we compare them they are always different pointers.
         */
        namesa[i] = d2i_GENERAL_NAME(NULL, &derp, gennames[i].derlen);
        derp = gennames[i].der;
        namesb[i] = d2i_GENERAL_NAME(NULL, &derp, gennames[i].derlen);
        if (!TEST_ptr(namesa[i]) || !TEST_ptr(namesb[i]))
            goto end;
    }

    /* Every name should be equal to itself and not equal to any others. */
    for (i = 0; i < OSSL_NELEM(gennames); i++) {
        for (j = 0; j < OSSL_NELEM(gennames); j++) {
            if (i == j) {
                if (!TEST_int_eq(GENERAL_NAME_cmp(namesa[i], namesb[j]), 0))
                    goto end;
            } else {
                if (!TEST_int_ne(GENERAL_NAME_cmp(namesa[i], namesb[j]), 0))
                    goto end;
            }
        }
    }
    testresult = 1;

 end:
    for (i = 0; i < OSSL_NELEM(gennames); i++) {
        if (namesa != NULL)
            GENERAL_NAME_free(namesa[i]);
        if (namesb != NULL)
            GENERAL_NAME_free(namesb[i]);
    }
    OPENSSL_free(namesa);
    OPENSSL_free(namesb);

    return testresult;
}

Project: openssl

static int set_cn(X509 *crt, ...)
{
    int ret = 0;
    X509_NAME *n = NULL;
    va_list ap;

    va_start(ap, crt);
    n = X509_NAME_new();
    if (n == NULL)
        goto out;

    while (1) {
        int nid;
        const char *name;

        nid = va_arg(ap, int);
        if (nid == 0)
            break;
        name = va_arg(ap, const char *);
        if (!X509_NAME_add_entry_by_NID(n, nid, MBSTRING_ASC,
                                        (unsigned char *)name, -1, -1, 1))
            goto out;
    }
    if (!X509_set_subject_name(crt, n))
        goto out;
    ret = 1;
 out:
    X509_NAME_free(n);
    va_end(ap);
    return ret;
}

Project: openssl

static X509 *make_cert(void)
{
    X509 *crt = NULL;

    if (!TEST_ptr(crt = X509_new()))
        return NULL;
    if (!TEST_true(X509_set_version(crt, 2))) {
        X509_free(crt);
        return NULL;
    }
    return crt;
}

Project: openssl

static int set_email_and_cn(X509 *crt, const char *name)
{
    return set_cn(crt, NID_pkcs9_emailAddress, name,
                  NID_commonName, "www.example.org", 0);
}

Project: openssl

static int call_run_cert(int i)
{
    int failed = 0;
    const struct set_name_fn *pfn = &name_fns[i];
    X509 *crt;
    const char *const *pname;

    TEST_info("%s", pfn->name);
    for (pname = names; *pname != NULL; pname++) {
        if (!TEST_ptr(crt = make_cert())
             || !TEST_true(pfn->fn(crt, *pname))
             || !run_cert(crt, *pname, pfn))
            failed = 1;
        X509_free(crt);
    }
    return failed == 0;
}

Project: openssl

static int is_exception(const char *msg)
{
    const char *const *p;

    for (p = exceptions; *p; ++p)
        if (strcmp(msg, *p) == 0)
            return 1;
    return 0;
}

Project: openssl

int setup_tests(void)
{
    ADD_ALL_TESTS(call_run_cert, OSSL_NELEM(name_fns));
    ADD_TEST(test_GENERAL_NAME_cmp);
    return 1;
}

Project: openssl

static int set_cn1(X509 *crt, const char *name)
{
    return set_cn(crt, NID_commonName, name, 0);
}

Project: openssl

static int set_cn2(X509 *crt, const char *name)
{
    return set_cn(crt, NID_commonName, "dummy value",
                  NID_commonName, name, 0);
}

Project: openssl

static int run_cert(X509 *crt, const char *nameincert,
                     const struct set_name_fn *fn)
{
    const char *const *pname = names;
    int failed = 0;

    for (; *pname != NULL; ++pname) {
        int samename = strcasecmp(nameincert, *pname) == 0;
        size_t namelen = strlen(*pname);
        char *name = OPENSSL_malloc(namelen + 1);
        int match, ret;

        memcpy(name, *pname, namelen + 1);

        match = -1;
        if (!TEST_int_ge(ret = X509_check_host(crt, name, namelen, 0, NULL),
                         0)) {
            failed = 1;
        } else if (fn->host) {
            if (ret == 1 && !samename)
                match = 1;
            if (ret == 0 && samename)
                match = 0;
        } else if (ret == 1)
            match = 1;
        if (!TEST_true(check_message(fn, "host", nameincert, match, *pname)))
            failed = 1;

        match = -1;
        if (!TEST_int_ge(ret = X509_check_host(crt, name, namelen,
                                               X509_CHECK_FLAG_NO_WILDCARDS,
                                               NULL), 0)) {
            failed = 1;
        } else if (fn->host) {
            if (ret == 1 && !samename)
                match = 1;
            if (ret == 0 && samename)
                match = 0;
        } else if (ret == 1)
            match = 1;
        if (!TEST_true(check_message(fn, "host-no-wildcards",
                                     nameincert, match, *pname)))
            failed = 1;

        match = -1;
        ret = X509_check_email(crt, name, namelen, 0);
        if (fn->email) {
            if (ret && !samename)
                match = 1;
            if (!ret && samename && strchr(nameincert, '@') != NULL)
                match = 0;
        } else if (ret)
            match = 1;
        if (!TEST_true(check_message(fn, "email", nameincert, match, *pname)))
            failed = 1;
        OPENSSL_free(name);
    }

    return failed == 0;
}

Project: openssl

static int set_email3(X509 *crt, const char *name)
{
    return set_cn(crt, NID_pkcs9_emailAddress, name,
                  NID_pkcs9_emailAddress, "dummy@example.com", 0);
}

Project: openssl

static int set_email1(X509 *crt, const char *name)
{
    return set_cn(crt, NID_pkcs9_emailAddress, name, 0);
}